Rochester single barrel - Impala Tech
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post #1 of 10 (permalink) Old 06-25-2012, 11:35 AM Thread Starter
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Rochester single barrel

(sounds like a whiskey doesn't it?)

Looking at eventually buying the Offenhauser Tri-power intake manifold for my 250 cu/in 6-shooter and I decided to start by sourcing a couple carburetors.

I've found a motley bunch on e-gay with different casting numbers and was wondering if that was enough to tell the difference in guts or if there would be other info needed?

The casting numbers in question are:
7027011 off of a 1967 chevy truck
and
7028168 off of a 1968 Pontiac

I looked at Rochester's numerical index and they both take "kit" part number: CK031 and float part number: F31 (if that helps any)

Either way, I'm trying to save from spending $180 a carb. If theres another source for used Rochesters I'm all ears

Thanks guys!
-Bill
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post #2 of 10 (permalink) Old 06-25-2012, 02:02 PM
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Bone yard. Every six banger had one. They cost about $21 each to rebuild. Three one barrel carbs on an intake work much better from a fuel distribution point of view than a four barrel carb does on a six cylinder manifold.

I recommend reading this book before you get started in doing anything to your six banger.
http://www.amazon.com/Chevrolet-Inline-Six-Cylinder-Power-Manual/dp/1931128154/ref=sr_1_sc_1?s=books&ie=UTF8&qid=1340647297&sr=1-1-spell&keywords=how+to+hot+rod+your+six+cylinder+chvrolet
Big Dave
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post #3 of 10 (permalink) Old 06-25-2012, 03:14 PM Thread Starter
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That's going on order as soon as I get home

As far as the bone yard goes, I'm up a paddle without a creek until my next visit to the states
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post #4 of 10 (permalink) Old 10-31-2012, 07:44 AM Thread Starter
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well, I finished the book. Modifying the 6-banger it seems a lot like swimming against the current.

Dollar for dollar, it looks like my money may be better spent on a small block (for simplicity, cost, and power output). Either way the engine swap is going to have to wait until I get back to the states to pursue. So in the meantime I think I'm going to take the money I was going to spend on the Offy intake and put it towards some suspension bits instead.

Good times!
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post #5 of 10 (permalink) Old 11-02-2012, 12:46 PM
 
 
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6 cyl

Hi,I ran that 3x1 intake on a 63 nova for 15 years ,tryed every trick in the book to make it run good ,did not happen. it only ran rich , got very poor performance unless wide open.It did get about 7 MPG on a good day .63 nova 230.cuin.040. over ,9.8 comp,1.94 valves .HEI dist super coil,2.5'' truck exhaust manifold &2.5 exhaust all the way out ,.............I put on an offy 4 bbl, intake 600 holley carb And it ran GREAT!!!!!!!!!!!!!!!!!!!!!!!!! 18 mpg,reved from 1000 to 6500 rpm smooth .somthing to think about. have fun with it....nolift
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post #6 of 10 (permalink) Old 11-02-2012, 02:09 PM Thread Starter
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Yeah, that was one of my worries was if the 3-pack doesn't run "as it should" I'm kind of on my own out here. Parts aren't readily available (usually takes 2-weeks to ship over from the states) and there isn't much in the way of mechanical help.

I took the money I was going to spend on the intake and bought a set of Hotchkis Swaybars from Summit for about $560.00. My buddy should be bringing them across the pond in about a week or so.
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post #7 of 10 (permalink) Old 11-02-2012, 05:21 PM
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Problem with three ones is you have three complete carbs. Three idle circuits to tune and three off idle transition circuits to equalize, three accelerator pumps and circuits to match, then you have to verify all three carbs see the same vacuum at WOT to tune your primary circuits.

With three two barrels only the center one has an accelerator pump or idle circuit. Everything else is just a vacuum controlled "back barrel" waiting for the engine to "need it".

It is the complexity of multiple carburation that changed my mind a long time about two fours being better than one big four barrel and the reason that I run only Holley brand carbs now. Back in the "good old days" you had to combine two Carter AFB's to get enough cfm flow to feed a hot 348 or 409. Because they were vacuum operated carbs they never gave that reassuring bog that comes from slamming open a bigger carb than your motor needs like you got with a Holley 950 cfm double pumper with full mechanical linkage.

I also had a rep as a hot rod mechanic and every one who had an exotic sports car would drag their Triumph Stag, powered by an unknown DOHC V-8 with four Webber side draft carbs, or Jaguar XKE six cylinder with three SU two barrels, or even a stone stock MG GT twin two barrel four cylinder car into my shop because they couldn't find any one else to tune their car. After a little quality time with an SU carb you soon learned to embrace the simplicity of a Holley four barrel.

There is a policy I learned a half century ago in the military. It is called KISS (not for Gene Simmon's band) but it stands for "Keep It Simple Stupid".

Big Dave
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post #8 of 10 (permalink) Old 11-03-2012, 03:21 PM Thread Starter
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Yeah, I'm a big fan of simplicity (and very familiar with K.I.S.S). After reading the "Inline 6 power manual" I came to the realization that if I really wanted to "make 6=8" (clifford quote there for ya) I was going to spend a bit of money and lose a lot of the simplicity. It seemed like my choices were either "turbo swap" (for high 200 hp range) or work the heads, cam, and internals to squeeze a lot of gas into a very small space and light it on fire (for low 200 range)

For the same money I can throw in a pretty mild 383 (I use the term "throw in" loosely) and easily break into the 400hp range without really stressing the internals at all.

but first: the suspension (then brakes, then motor/transmission...)

Good times
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post #9 of 10 (permalink) Old 11-03-2012, 04:56 PM
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That is very true but how many people have a tricked out six compared to a 383 (Chevy guys have made more of them than Chrysler ever stuffed into Road Runners or big Dodges).

It only takes about seven horsepower to push your car down the road at 40 mph (which is why an OD is so important as you don't need a lot more power to cruise at a higher speed so a V-8 running just a bit faster than at an idle can make more than enough power to keep you happy cruising with an OD tranny). You want a big American V-8 only to accelerate quickly (it is the torque the motor makes that pushes you back in your seat). If you are only going to cruise a L-6 can more than meet your needs.

Big Dave
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post #10 of 10 (permalink) Old 11-13-2012, 04:46 PM Thread Starter
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You're right about the 383 and I would love the "oh crap" factor of having a speedy six-shooter...

I dunno, it's still a long way off... I stood on the brakes today (4-wheel drum) and I think that needs to be the focus of my attention first. My mind will probably change 20 more times before I get to messing with the engine. (I have the worst automotive ADD)

Good times!
-Bill
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